Carburetor



Aug. 7, 1928.

W. B. RALSTON CARBURETOR Filed May 21, 1920 I I 2 Q M M INVENTOR.

ATTORNEY;

Patented Aug. 7, 1928.

UNITED STATES PATENT OFFICE.

camzunn'ron.

Application filed May 21,

This invention relates to improvements in carburetors for internal combustion engines, and the objects thereof are: First, to provide a construction in which liquid fuel is first atomized, mixed with a small quantity of air and subjected to the action of heat and subsequently mixed with an additional and larger body of air previous to its admission to the engine; second, to provide asensitive mechanism for regulating the admission of liquid fuel to the carburetor which is effected directly more or less by the volume of air admitted to the mixing chamber; third, to provide a construction which permits of placing part of the mixing chamber directly in the path of the engine exhaust to be heated thereby; fourth, to so construct the device that the liquid fuel Will be maintained at normal temperature until it is atomized and mixed with air preparatory to being vaporized by the application of heat; fifth, to so arrange the parts of the device that surplus liquid fuel will drain into the intake manifold and obviate flooding of the carburetor; and sixth to so construct and arrange the parts of the device as to afford a compact and easily assembled unit.

The objects of the improvement are accomplished by the construction illustrated in the accompanying drawings in which:

Fig. 1 is a side elevation of the device positioned in connection with the exhaust and intake manifolds of an engine, there being parts broken away;

Fig. 2 is a. vertical section in a central plane through Fig. 1;

Fig. 3 is a plan view of Fig. 1;

Fig. 4 is a vertical section through the mixing chamber in a central plane through the air inlet;

Figs. 5 and 6 are detail views of the adjustable fulcrum for the needle-valve actuating. lever, showing a side and end elevation of the same respectively.

Similar characters ofreference indicate corresponding parts throughout the several views and referring now to the same:

1 is the exhaust manifold of a gas engine, and 2 is the intake manifold thereof. 3 is a casting, forming the body of the carburetor and provided with a mixing chamber 4 havifig a projecting cylindrical extension 5 at one end'thereof, and having an outlet con- 1920. Serial No. 388,120.

nection 6 leading downwardly from the mixing chamber into the intake manifold in which is located a-throttle-valve 7 The end 5 of the body, in which is located part of the mixing chamber, projects through an opening 8 made in the exhaust manifold, into the interior thereof directly in the path of the exhaust so as to become heated thereby. An air inlet member 9 has communication with the chamber 4 at the top of the chamber. and in the upper end of the member is positioned an air inlet valve 10 which is normally forced toward its port by a spring 11. A forked lever 12 is pivotally arranged so as to engage a flanged sleeve 13 on the stem 14 of the valve by means of which the spring 11 may be adjustably compressed.

The chamber 4 is closed at its front end by a head 15 which has a pipe 16 that extends through the center of the chamber 4 and terminates near the inner end thereof in a. flaring flange 17, there being a space 18 intervening between theflange and the adjacent end wall 19. The head has a hollow stem 20 having connection with the pipe 16. and also air inlet openings21. A nozzle 22 projects into the stem, and a needle-valve 23 is arranged in the stem for regulating the flow of liquid fuel through the nozzle. A collar 24 has threaded connection with the needle-valve at the upper end thereof. and a spring 25 acts against the collar and tends to hold the needle-valve closed. On each side of the pipe 16 is a partition 26 that extends from the head into the chamber 4 to a suitable distance so that the chamber is partially divided horizontally.

An air-flow valve 27 is looselv positioned in the air inlet member 9 between the valve 10 and the mixing chamber 4, and consists of a shell with a closed lower end 28 with large openings 29 in its sides, the shell fitting loosely in the member 9 so as to move therein with freedom. The air-flow valve rests upon the upturned end of a lever 30 that extends into the mixing chamber. the outer end of the lever being positioned so as toengage the lower end of collar 24. The stem of the valve 23 extends loosely through the forward end of the lever 30 and thereby the latter is held in position upon its fulcrum 31. A sliding bar 32 extends through the head into the chamber and the i chamber.

fulcrum 31 is formed at its inner end. A thumb-nut 33 on the threaded outer end of the bar is provided for its adjustment. Thus, the fulcrum may be adjustably shifted so that the needle valve will be raised more or less proportionately with the movement of the air-flow valve.

A vertically sliding bar 34 is provided with-a finger 35 that is adapted to engage the collar 24 at the lower end thereof so that the needle-valve may be raised by ,shifting the bar upwardly. A wire 36'is connected to the bar 34, and-a wire 37 with the lever 12 by means of which the bar and lever may beoperated from any convenient point.

The stem 20 is connected at its lower end with a float chamber 38 by means of which liquid fuel is'supplied to the nozzle, the chamber being of theusual construction.

In the operation of the invention the liquid fuel passing out of the nozzle 22 is atomized and drawn with air admitted through the air inlet openings 21 through the pipe 16 into the mixing chamber 1. The air entering the inlet openings 21 tends to keep the nozzle cool. As the mixture thus formed is drawn through the space 18 between the flange 17 and the end wall 19 into the mixing chamber, all of t-he atomized liquid is thus brought into close proximity to the end wall which is heated by the ex-.

.haust passing through the exhaust manifold, and thereby becomes vaporized'in its passage from the ipe 16 into the mixing As the throttle-valve 7 is opened, the content of the mixing chamber is drawn into the intake manifold owing to the suction of the engine, and air is admitted into the mixing chamber through the air inlet member 9, after passing the air inlet valve 10. The passage of air through the member actuates the air-flow valve 27 to a more'or less extent, depending upon its volume, and the lever 13 becomes correspondingly tilted upon its fulcrum causing the needle-valve 23 to accordingly rise, thereby permitting liquid fuel to pass out of the nozzle.- It is essential that the spring 25 on the needle-valve be such that the air-flow valve will be held with greater sensitiveness than the air inlet valve is held by its spring, so that the action of the air-flow valve will be directly proportionate with the volume of air admitted by the air inletvalve independent of the spring adjustment of the latter. There is thus provided a more or less lag relation between valves 27 and 10, the valve 27 being responsive to the variations in suction values in the mixing chamber in ad-' vance of and with less resistance than valve 10. The sensitiveness of valve 27 thus not only provides for more efficient control of valve 23, enhancing the picking up value of the carburetor, but it provides for a closer proportioning of air and fuel to meet the demands. Thus the quantities of liquid fuel and air admitted to the carburetor is maintained in a constant ratio. By adjustably shifting the fulcrum, the ratio of movement between the needle-valve and airflow valve may be altered so that the quan-.

tity of atomized liquid fuel'may be properly proportioned with the volume of air drawn into the mixing chamber through the air inlet member. The air admitted to the mixing chamber through the inlet member 9 is diverted by the partitions toward the heated end of the chamber and there unites with the entering mixture of vaporized fuel and air preparatory to its passage to the intake manifold.

The construction as shown in the drawing is such that should the fuel in the mixing chamber become ignited by back-fire from the engine, the pressure thereby occasioned in the mixing chamber causes both the airflow valve and air inlet valve to raise so as to prevent escape of flame out through the air inlet, and owing to the narrowness of the space 18 between the flange 17 and end wall 19 the flame becomes choked and extinguished as the pressure in the mixing chamberis relieved back through the pipe 26 and out the openings 21.

A feature of the invention is in the relative arrangement of the atomizing means and vaporizing means at opposite ends of the mixing chamber while the air inlet and the outlet are located between the two means so that the air entering the mixing chamber tends to keep the atomizing means cool, which action is augmented by air admitted through the openings 21. Thus, all of the;

air entering the carburetor is utilized to keep the atomizing structure at a sufficiently low temperature as to insure entrance of the fuel through the nozzle in a liquid state. This structure allows fuel to be admitted in proper proportions, which would be impossible if the temperature of the nozzle reached a point sufficiently high to vaporize the fuel before passing the needle valve.

As the mixing chamber is positioned above the intake manifold, with its outlet port leading from its bottom, any liquid fuel that may be drawn into the mixing chamber without becoming vaporized drains into the intake manifold and thereby flooding of the mixing chamber is avoided.

As will be seen, in the normal or closed position of valve 10, its port is not entirely closed, there being open communication between the atmosphere and the chamber be tween valves 10 and 27, whether valve 10 be in its normal or relatively closed position or is shifted from this position by the action of the engine; when valve 27 is in its closed position, the chamber between the valves is at atmospheric pressure due to this permanent communication characteristic around valve 10. For purposes of explanation the chamber between valves and 27 will be called an entry chamber.

As heretofore pointed out, spring 25 is weaker than spring 11, and the two valves 10 and 27 are independent of each other structurally, there being no mechanical connection between the valves such as would cause movement of valve 27 to force movement of the valve 10; functionally, however, the movement of valve 10 is responsive to movement of valve 27 under predetermined conditions.

As a result of this construction, the carburetor produces certain results. Assume, for instance, a condition in which the depression within the mixing chamber is insuificient to overcome the resistance of spring 11a condition which may be present during idling. During this period the underside of valve 27 is subject to the pressure then present in the mixing chamber while the upper side of the valve is subject to the pressure within the entry chamber, the latter receiving air leaking past valve 10; since the pressure on the outer side of valve 27 is greater than that on the inner side, the valve will move inward to the extent permitted by spring 25., thus opening communication between the mixing and entry chambers. At this time, therefore, the pressure in the entry chamber is neither atmospheric nor that of the mixing chamber, but a pressure between,

the two approaching somewhat the pressure within the mixing chamber.

This condition can be explained theoretically although the exact action which takes place in producing the result is unknown. With the entry chamber at atmospheric pressure-valve 27 being in closed positionany pressure reduction in the mixing chamber produces a difierential between pressures on opposite sides of valve 27; when this differential is sufficient to overcome the resistance of spring 25, valve 27 will move inward and open communication between the mixing and entry chambers, tending to equalize the pressures in the entry and mixing chambers; if valve 10 were entirely-closed, this equalization would be complete whereupon spring 25 would close valve 27. However, the leakage of air past valve 10 intothe entry chamber prevents this total equalization between the two chambers, and valve 27 will assume a position determined by the leakage port around the valve 10. the area of the valve 27 and the pressure of the spring 25, with the pressure within the entry chamber between that of the mixing chamber and differential between the atmosphere and the pressure in the entry chamber.

When the throttle isopened, the depression at first increases in the mixing chamber, and the increased differential between the mixing and entry chambers causes valve 27 to shift inwardly a greater distance. This movement reduces the differential between the two chambers by a depression increase in the entry chamber and the decrease in the mixing chamber, and further causes an increased. differential bet-ween the opposite sides of valve 10 sufiicient to overcome spring 11 and open valve 10. With valve 10 open, the strength of spring 11 becomes another factor in determining the position of valve 27. The condition to be satisfied under the changed conditions is still that the amount of air passing the valve 27 is the same as that passing the valve 10.

This condition involves the openings of the valves 10 and 27, which are determined by the size of the valves, the strength of their respective springs 11 and 25 and the differential between the atmosphere and the entry chamber and that between the entry chamber and the mixing chamber, which cause flow of air through these openings. The position of valve 27 depends upon the pressure on the valve due to the differential between the entry and mixing chambers and the resistance of the spring 25, but obviously must difler from the idling position, as more air must be allowed to pass.

The advantage of my arrangement is this. 1 0 In devices of the prior art, the fuel valve has been connected with the air valve corresponding to my valve 10, the spring of which has to resist the full differential between the atmosphere and the mixing chamber and has \05 to be comparatively stiff and insensitive, By dividingthis differential by the use of the entry chamber of my device, I am enabled to make the spring 25, which directly controls the fuel valve, much lighter and eon- 110 sequently more sensitive to slight variations in the mixing chamber pressure. In addi-' tion, the pressure differential between the entry chamber and the atmosphere does not reach that between the mixing chamber and 115 the atmosphere, and hence the resistance of spring 11 need not be as great=as under the latter conditions, so that valve 10 also becomes more sensitive in action and more responsive to smaller variations in entry cham- 12o berpressures. It will thus be seen that neither valve 10 nor valve 27 is subjected to the pressure diiferential between the at; mosphere and the pressure within the mixing chamber; that differential is present, of 125 course, but neither of these valves is re quired to meet the conditions produced by it, since the intermediate pressure of the entry chamber serves to limit the difi'erential across the valve individually;

This sensitive control is particularly advantageous where the carburetor is of a type in which the initial charge is formed remote from the mixing chamber in order to gasify such charge in advance of delivery to the mixing chamher,a condition which requires that the gasifying structure and the chargeforming structure be remote from each other; under such conditions there is necessarily a delay between the movement of the air valve and the change in the character of the charge supply to the engine through the travel of the initial charge from the initial forming point to the mixing chamher-any material lag in the response of the fuel valve to depression changes in the mixing chamber has the effect of prolonging this lag.

It has already been proposed to use a detector structure in connection with an auxiliary air valve, the detector structure being more sensitive than that of the air valve. While this structure is more sensitive to changes in pressure within the mixing chamber than where the fuel control is connected directly to the air valve, the arrangement still presents the disadvantage that the detector is also subject to the differential be tween the mixing chamber and the atmoshere. A low resistance Would bring the full stroke of the detector with but small depression increase in the mixing chamber and thus provide an excess delivery of fuel, while an increase of resistance to meet this condition would necessitate an increased depres sion to overcome the resistance, thus producing the delayed action previously referred to. While valve 27 in the present structure acts as a detector of pressure variations in the mixing chamber, it is subject only to the differential between the entry and mixing chambers, and hence the resistance of spring 25 can be comparatively low and thus provide for fuel Valve changes rapidly and without producing abnormal movements thereof.

It will be understood, of course, that valve 10 primarily controls the depression within the mixing chamber, valve 27 having no material efiect in this connection excepting that which comes incidentally through its control of the communication between the two chambers. IVith the permanent communication between the entry chamber and the atmosphere, spring 11 can be arranged to deter mine the desired depression within the mixing chamber without being required to consider the control of the fuel supply, the latter being the function of valve 27 and spring 25.

What I claim is:

1. In a charge forming device for an internal "combustion engine having inlet and exhaust pipes and means for producing an initial mixture of air and fuel; a mixing chamber havin an inlet for the bulk of the air supply an also a portion of the walls thereof extending into an opening in the wall of said exhaust pipe, a conduit of comparatively small cross-section extending from said initial mixture-forming means across said mixing chamber and terminating in an enlarged head of a shape similar to the cross section of the wall portion of the mixing chamber so extending into the exhaust pipe, so as to leave a narrow passage between said head and the adjacent walls of themixing chamber, and also having battles on its sides arranged transversely to the line of flow of the bulk of the air supply so as to direct said air against the interior of said enlarged head and across the line of flow of the heated mixture leaving said narrow pas sage, for heating said initial mixture and diluting it with the bulk of the air necessary for combu 'tion.

2. In a charge forming device for an internal combustion engine having inlet and exhaust pipes and means for producing an initial mixture of air and fuel; a mixing chamber having an inlet for the bulk of the air supply and also having a portion of its walls positioned relative to the exhaust pipe to be heated by the gases passing through raid pipe. a conduit of comparatively small cross-section extending from said initial mixture-forming means across said mixing chamber and terminating in an enlarged head of a shape similar to the cross-section of the wall portion of the mixing chamber being heated by the exhaust, so as to leave a narrow passage between said head and the adjacent walls of the mixing chamber, and also having baflles on its sides arranged transversely to the line of flow of the bulk of the air supply so as to direct said air against the interior of said enlarged head and across the line of flow of the heated mixture leaving said narrow passage, for heating said initial mixture and diluting it with the bulk of the air necessary for combustion.

3. A carburetor comprising a mixing chamber, means for discharging fuel into said chamber, means controlling the amount of fueldischarged, two suction-responsive valves mounted in the air inlet to said mixing chamber and forming between them an entry chamber, the outer of said valves restricting, but not closing, the air inlet and having a greater resistance to opening than the inner valve, and means whereby the opening of the inner'valve opens the fuel controlling means.

t. In carburetors, a mixing chamber, means for discharging fuel into said chamber, means controlling the amount of fuel discharged, an air inlet for the mixing chamber independent of the fuel delivery to such chamber, suction-responsive means for controlling the passage of air through said inlet, said latter means comprising valves located to form an entry chamber Within the inlet with the entry chamber permanently open to the atmosphere, the valves having such relative resistances to openin as to cause the pressure Within the entry c amber I to be intermediate the pressure Within the mixing chamber and the atmospheric pressure, whereby the pressure drop across each 

